1. Field
The present invention relates to a microphone, particularly to a microphone in which an acoustic sensor is mounted on a main surface of a base substrate.
2. Related Art
A microphone is used in various devices such as a mobile phone and an digital voice recorder. For example, in the microphone disclosed in U.S. Pat. No. 7,763,972, an acoustic sensor and a circuit element are stacked, the acoustic sensor includes a thin film acting as a sensor unit, and the circuit element includes a cavity formed at a position corresponding to the thin film.
Nowadays, there is a demand for further downsizing in the microphone, particularly there is a demand for a low profile in which a whole height of the microphone is reduced. A distance between a sound hole communicating with an outside of the microphone and the sensor unit decreases when the height is reduced for the purpose of the low profile as disclosed in U.S. Pat. No. 7,763,972. Therefore, unfortunately an acoustic characteristic of the microphone is degraded due to a foreign matter invading into the microphone through the sound hole, and the sensor unit is easily broken due to compressed air flowing into the microphone through the sound hole.
U.S. Patent Application Publication No. 2007/0278601 discloses a device having a configuration in which external interference is prevented by bending an acoustic port in a substrate.
In the device disclosed in U.S. Patent Application Publication No. 2007/0278601, the substrate is required to have a thickness for forming the acoustic port having the best shape inside the substrate. Therefore, there is a limitation to the reduction of the substrate thickness, which results in the low profile of the whole microphone being difficult to achieve.